How to Load and Manage PDF Documents in .NET

Overview

This guide covers opening, creating, and saving PDF documents using the core Document class.

Prerequisites

Requirement	Detail
Runtime	.NET 8.0 or later
Package	Install via `dotnet add package`

Open a PDF from bytes

Load an existing PDF into a Document instance by passing a byte array to Document.Open. This approach avoids file locks and works well for in-memory workflows such as web request handlers.

using var doc = Document.Open(File.ReadAllBytes("input.pdf"));
Console.WriteLine($"Pages: {doc.Pages.Count}");

Create a new document

Instantiate an empty Document, add at least one page, and call Save to produce a valid PDF file on disk.

using var doc = new Document();
doc.Pages.Add();
doc.Save("new.pdf");

Modify page geometry

Access a page by its 1-based index and set the media box, crop box, or rotation. The Rectangle constructor takes coordinates in the order left, bottom, right, top.

var page = doc.Pages[1];
page.SetMediaBox(new Rectangle(0, 0, 612, 792));
page.SetRotation(90);

Add a file attachment

Embed a file into the PDF using FileSpecification. The embedded file appears in the viewer’s attachment panel and can be extracted by recipients.

var spec = new FileSpecification("data.csv", "Embedded data");
doc.EmbeddedFiles.Add(spec);
doc.Save("with-attachment.pdf");

Key Classes

Class	Purpose
`Document`	Root PDF object
`Document.Open`	Open from byte array
`Page`	Single page with content and geometry
`PageCollection`	Manage document pages
`FileSpecification`	File attachment descriptor